Pakistani Prime Minister Nawaz Sharif has defended his financial record and asked parliament to form a commission to investigate allegations stemming from the Panama Papers leak.

Sharif told parliament on May 16 that his wealth was acquired legally before he entered politics and at no time did he take state money offshore.

"I can say with surety that...not a single penny went out of Pakistan," he said.

Sharif has been under pressure since documents released as part of the Panama Papers data leak showed his children owned several offshore companies and used them to buy properties in London.

He and his children deny any wrongdoing, though the opposition has seized on the Panama Papers scandal as an opportunity to try to unseat Sharif.

The prime minister said his father built up the family business before he entered politics and established a steel mill abroad while he was in exile. The Jeddah steel mill was then sold in 2005 for $17 million, and the proceeds were used to buy the apartments in London, Sharif said.

He also presented details of his and his family's tax affairs -- the latest of a series of disclosures he has made since the Panama Papers were leaked.

A previous disclosure on May 13 that he once owned an offshore company to buy a London flat and avoid paying British taxes appears to have taken some of the wind out of the opposition's plans to use the Panama Papers revelations to tarnish Sharif.

With new details coming to light, Sharif asked the opposition and other lawmakers to help form a parliamentary commission to investigate the matter.

Previous efforts to have a retired or sitting Supreme Court judge chair a judicial commission have stalled as all the judges rejected the offer.

It is not clear if the opposition will take up Sharif's latest offer. They walked out soon after Sharif stopped speaking.

The opposition argued that the judicial probe should largely focus on Sharif's family, though the leaked papers have also named other Pakistani politicians and businessmen alleged to have substantial undeclared overseas assets.

Opposition leaders say they are angry that Sharif didn't provide details they were seeking in seven questions they posed to him ahead of the parliamentary session, including details on the money trail leading to his overseas properties.

"Not a single question has been answered," said Khursheed Shah, leader of the opposition in the National Assembly.

Opposition politicians said they would announce on May 17 their response to Sharif's speech.